NEW YORK — If you look for it, there’s a lot of stuff packed into “The Grinder,” a funny if — at first glance — lightweight comedy starring Rob Lowe and Fred Savage.There’s brotherly love. Sibling rivalry. A quest for authenticity by someone used to profiting from make-believe. A spoof of celebrity. And a not-implausible argument that effective jurisprudence is as much based on theatrics as the law.Premiering this past Tuesday on Fox, “The Grinder” finds big-time TV …